| 年度 | 实际值 |
|---|---|
| 1993 | 23 |
| 1994 | |
| 1995 | 19.4 |
| 1996 | 17.8 |
| 1997 | |
| 1998 | |
| 1999 | |
| 2000 | 3.3 |
| 2001 | 1.06666666666667 |
| 2002 | |
| 2003 | 8.26 |
| 2004 | 9.95 |
| 2005 | 11 |
| 2006 | 11.5 |
| 2007 | 13.4 |
| 2008 | 14.48 |
| 2009 | |
| 2010 | 15.52 |
| 2011 | 19.7 |
| 2012 | 24.63 |
| 2013 | 31.13 |
| 2014 | 32.11 |
| 2015 | 33.7 |
| 2016 | 36.32 |
| 2017 | 37.06 |
| 2018 | 38.03 |